I have a 4TB disk I have used for about a year (never been defragged). When I ran Windows own defrag it said that only 3% where fragmented. but defragmenting didn't run (stuck at 0%).
Then I tried the Defraggler. And it said that 87% of the files where fragmented.
So I started the defrag (with Defraggler) and the first 8% took about 2 hours for each %. But from 9+% it has taken like 8-9 hours per %. it has been running for 2½day now. and only 12% defragged.
The drive has like 1TB pics and 2TB video/music files.
My system is not running anything else (closed all non-essential programs)
The drive is my D:/ non OS drive only data storrage
My question is, is it normal that its farster in the beginning, and then slows down ?
From my understanding on a traditional mechanical hard disk with moving parts the access speed and write speed will be faster near the beginning of the disk. That's why defrag software tries to move programs and operating system files near the beginning of the disk so programs will load faster, and Windows will startup faster. The further down it gets into the defrag map the closer it gets to the slower areas of the hard disk.
Perhaps it is the antivirus software causing the excessive slow speed. Some antivirus scanners will scan every file moved during a defrag therefore temporarily disabling the antivirus real-time protection may allow it to defrag faster. Then again allot of modern antivirus scanners know to calm down when a defrag is taking place at least they do with the built in Windows defrag.